Control switch having high pressure safety mechanism



March 19, 1940. B. E. SHAW 2,194,127

CONTROL SWITCH HAVING HIGH PRESSURE SAFETY MECHANISM .Filad Jan. 3; 19:9 2 Shuts-Sheet 1 INVENTOR.

ATTORNEY 5 March 19, 1940. B. E. SHAW 2,194,127

CONTROL SWITCH HAVING HIGH PRESSURE SAFETY MECHANISM Filed Jan. 3, 1939 2 Sheets-Sheet 2 1 a E 4,01,; N v /25 f E i kw. (I? I H ,1

33 E j? flu l w 53 IN VENTOR.

ATTORNEY 5 Patented Mar. 19, 1940 UNITED STATES PATENT oer-Ice CONTROL SWITCH navmo men rans- Electric Switch 00..- tion of Iowa Goshen, Ind., a corpora- Application January 3, 1939, Serial No. 248,974

BCIaims.

An object of my invention is to provide a simple and inexpensive control switch having a novel safety mechanism responsive to abnormal pressures for opening the circuit through the switch.

A further object is to provide safety mechanism includingtoggle mechanism operable to throw the switch arm to open circuit position, a

latch for latching the toggle mechanism in open.

circuit position and. a manual reset button or trip means for said latch to permit the toggle mechanism to return to normal position providing the abnormal pressure has changed to normal pressure.

A further object is to provide a control switch in which a magnet or equivalent means constrains the switch to remain in closed position but it will remain in open circuit position if thrown to that position by the normal operating means, there being a spring connection between the switch arm and the normal operating means to permit the switch to be moved to open circuit position by the safety mechanism independent of the normal operating means.

Another object of my invention is to provide safety mechanism which is particularly designed to cooperate with a control switch of the char acter referred to in the preceding object in such manner that toggle mechanism of the safety mechanism throws the switch to open circuit position and it cannot be returned manually to closed circuit position unless an abnormally high pressure which operated the toggle mechanism has receded and the normal operating means of the control switch is also in position calling for a closed circuit operation of the switch.

Still another object is to provide a control switch including a switch arm and an auxiliary switch arm connected together in such manner that the contact pressure of the switch contacts controlled by the switch arm remains substantially constant and the resilient connection also permits of the possibility of the toggle mechanism of the high pressure safety control mechanism to move the switch to "off position even when the auxiliary switch arm remains in closed circuit position.

Other objects, benefits and characteristic features of the present invention will be in part ob- 0 vious from the accompanying drawings and in (0:. zoo-as) upper portion of the structure as taken on the line 2-2 of Figure 4.

Figure 3 is a similar view showing various parts of the apparatus in different positions.

Figure 4 is an enlarged sectional view on the line 4-4 of Figure 1 showing a plan view of the control switch and safety mechanism, and

Figure 5 is a vertical sectional view on the line l! of Figure 3 to illustrate the association and relation of various parts of my switch structure. 0n the accompanying drawings I have used the reference numeral it to indicategenerally a housing or casing for the switch mechanism. A pair of bellows housings-l2 and i3 are secured thereto and within them are located pressure.

responsive bellows i4 and I 6.

The bellows it is responsive to normal pressures such as the pressures developed in the low pressure line of a mechanical refrigerating system. A conduit I6 is provided for connecting the interior of the housing 12 with such low pressure line so that the bellows M is responsive to pressure therein.

Within the housing Hi I provide a bracket ll carrying a pivot pin ID. A bell crank lever I9 is pivoted thereto and is adapted to be actuated by a pin 2|! extending from the head of the bellows I4. I

A supporting bar 2| is located within the housing l0 and supports a permanent magnet 22 and a bracket 2!. The magnet 22 is retained in position by a bracket 24 carrying stationary contacts 25 and 28. A switch arm 21 is pivoted on a pin 28 carried by the bracket 23. The switch arm is provided with contacts 29 and 30 adapted to coact with the contacts 25 and 28 for 'closing an electric circuit between terminals 3| and 32. The magnet 22 acts on the switch arm 21 (which is made of iron or the like so as to constitute an armature) to normally retain the contacts 25, 28, 26 and 30 engaged with each other.

An auxiliary'switch arm 33 is pivoted on the pin 28 and is constrained normally to move upwardly by a spring 34. The auxiliary arm 33 is provided with a slot 35 in which a head 36 of a rod 3'! slides, The rod 31 is connected by'a sleeve-38 to a pivot screw 89 which in turn is carried by a leaf spring 40 riveted to the bell crank lever is. A range adjusting spring 4| is connected with the bell crank lever for adjusting the range of operation of the bellows l4.

Referring to Figure 2, a spring 42 is provided which normally constrains the switch arm 21 to engage a bead 48 of the auxiliary switch arm 33. When the auxiliary switch arm is in the closed circuit position shown in Figure 2, the switch contacts are engaged under substantially constant return of the auxiliary switch arm toward closed circuit position. a

Within the bellows housing iii, the comparatively small bellows I5 is responsive to an abnor- ,mally high pressurein a pipe line 34. The line 44 is connected (in the case of a refrigeration control system) with the high side of the compressor so that abnormally high pressure therein will be transmitted to the bellows E5. The bellows l5 however may be designed for any abnormal pressure depending on the particular installation where the switch is to be made.- An operating pin 45 (see Figure 2) extendsfrom the head of the bellows l5 and coacts with a cross member or web 86 of a channel-shamd lever, the flanges of which are indicated at all and if). The flanges ti and 48 are pivoted to a pin t9 which in turn is supported rigidly relative to the casing l@ by V a bracket Bil.

The web 46 is provided with a sleeve-like portion St between which and an adjusting nut a spring 53 is positioned. The nut 52 is carried by a threaded rod 5 extending through the sleevelike portion 5i and anchored relative to the casing Iii. Thenut 52 may be adjusted for varying the range of operation or" the bellows 95 as de= sired.

The flange-like arm 38 is part of a toggle mech anism which includes a U-shaped toggle'lever having a pair of spaced sides or arms 55 and an end, member 56. A spring bl is connected between the end member and the arm lll. 18etween the two connections the arms 55 are provided with knife edged projections 58 seamd in V-seats 5s. The V-seats 59 are formed in per tions 50a of the bracket 56 It will be noted by referring to Figure 2 that the center line of the spring Si is below the pivotal point of the knife edged projections 5t and their seats 59. Whenever the outer end of the arm 48 is moved to the full line position of Figure 3, by excessively high pressure acting on thebellows I5, the spring is moved across the center line which throws the toggle lever 55-56 upwardly to the position shown where it stops against a projection 50b of the bracket 50. In moving to this position, aprojection 480: on the arm 48 engages a latch 60 and swings it about its pivot 6| to the position shown by full lines in Figure 3. The pivot 6! is carried by one of the portions 50a of the bracket 50 as shown in Figure 5 and a spring 62 is mounted on the pivot SI for the purpose of biasing the latch toward its latched position as shown by dotted lines in Figure 3 which it assumes when the pressure on the bellows l5 recedes.

For releasing the latch 60 I provide a reset button 63 mounted in a sleeve 64 projecting from the housing "I. The knob operates a pin against the action of a spring 66 to move the latch 60 to unlatched position as shown by dotted lines in Figure 2.

Practical operation During the normal operation of the refrigeration system, the bellows l4 will move between predetermined limits as determined by the range spring 4|. As the pressure decreases, the rod n will be pushed upwardly to take up the lost motion of the head 36 in the slot 35 and then cause the auxiliary switch arm 33 to press at the point 43 on the switch arm 21 and swing the switch arm to open circuit position where it is constrained to stay by the spring 34. I

When the pressure-increases against the bellows l4, the head 38 moves downwardly in the slot 35 until the lost motion is taken up and then the auxiliary switch arm 33 is moved downwardly with the switch arm 27 following it, due to the action of the spring 42 keeping the switch arm 27? engaged with the bead 43.

When an excessively high pressure is developed in the pipe line 44, the bellows l5 will move the arm 43 to the full line position of Figure 3, thus causing the toggle lever 55 to engage an extension 21a of the switch arm 2V and throw the switch arm to the-open position shown by dotted lines against the bias of the light spring 42. This quickly separates the switch contacts to .rninimlze arcing and thereafter, the spring 42 will return the switch arm 27 to the fullline position with the contacts still separated but not so widely. The extension 21a is preferably of insulating material.

Subsequently, when the pressure on the bellows l5 recedes'the arm 48 will be latched in the dotted position shown in Figure 2 with the toggle arms 55 still in raised position because the toggle spring 5? is above the pivot point of the knife edged extensions 58 in the V-seats so.

. After the parts are in the dotted position of Figure 3, the reset button 53 may be pressed inwardly to the dotted position of Figure 2 which swings the latch 60 to the dotted position shown in that figure and the arm 48 will then return to the full line position. If however the pressure on the bellows I 5 has not receded, the arm 48 will remain in the full line position of Figure 3 and operation of the latch 60 by depressing the reset buttons 63 will not be able to efiect any movement of the toggle lever 55 to position which permits the switch arm to move to its closed position. Therefore manual closing of the switch cannot be accomplished if there is still an excessively high pressure in the bellows housing I3.

Likewise the switch cannot be closed if the pressure against the bellows i4 is high enough to hold the auxiliary switch arm 33 in open circuit position. In that case, even though the toggle lever 55 is returned to its initial position, the auxiliary switch arm 33 will retain the switch arm 21 in open circuit position and not permit manual movement thereof to closed position.

Having described one specific embodiment of my control switch together with the operation thereof, I desire it to be understood that the form selected for description in the specification is merely to facilitate the disclosure of the invention and not to limit the details as to the form which it may assume. It is to be further understood that various modiflcations, adaptations and alternatives may be applied to the specific form disclosed to meet the requirements of practice without in any way departing from the spirit and purpose of my invention and the scope thereof as set forth in the appended claims.

I claim as my invention:

1. In a control switch having abnormal pressure safety mechanism, a common pivot pin. a switch arm pivoted thereon, an auxiliary switch arm also pivoted thereon, a permanent magnet for constraining said switch arms to assume closed'clrcuit positions, spring means operable to retain said switch arms in open circuit position against the bias of said magnet when said switch switch arm is in closed circuit position, pressure responsive means normally operable to pivot said switch arms to open and closed circuit positions and retain the switch contacts controlled by the switch arm in substantially constant pressure contact with each other when in closed circuit position, a second pressure responsive means responding to an abnormal pressure to pivot said switch arm relative to said auxiliary switch arm to open circuit position against the constraint of said resilient connection; a latch for retaining said second pressure responsive means in open circuit position, a manual release ior s'aid latch, spring means returning said pressure responsive means to normal position upon release of said latch providing the abnormal pressure has changed to normal, said auxiliary switch arm retaining said switch arm in open circuit position unless said first pressure responsive means is of a pressure value to permit said switch arm to be returned to closed circuit position by said resilient means.

2. In a refrigerator control switch having excessively high pressure safety mechanism, a switch arm, an auxiliary switch arm, means responsive to the pressure in the low side of the refrigerator for operating said auxiliary switch arm, a. permanent magnet constraining said switch arms to assume closed circuit positions, spring means operableto retain said switch arms in open circuit position against the bias-of said magnet when said auxiliary switch arm is moved to open circuit position by said responsive means, a resilient connection between said switch arm and said auxiliary switch arm whereby said switch arm can be moved relative to said auxiliary switch arm to open position while the auxiliary switch arm is in closed circuit position, pressure responsive means normally operable to move said auxiliary switch arm between open and closed circuit positions, a second pressure responsive means responding to an abnormal pressure to move said switch arm relative to said auxiliary switch arm to open circuit position against the constraint of said resilient connection, a latch for retaining said abnormal pressure responsive means in open circuit position, a manual release for said latch and means returnin said pressure responsive means to normal position upon release of said latch providing the abnormal pressure has changed to normal.

3. In a control switch having pressure safety mechanism, a switch housing, a switch arm therein, an auxiliary switch arm having a spring connection with said switch arm to provide substantially constant contact pressure between the contacts controlled by said switch arm when said auxiliary switch arm is in closed circuit posi tion, and means operable to move said switcharm to open circuit position when said auxiliary switch arm is in closed circuit position, said last means comprising toggle mechanism in said housing, said toggle mechanism including a bell crank having one arm lying along one wall of said housing and responsive to abnormal pressure and its other arm extending along another wall of said housing at right angles to the first wall, means to latch said toggle mechanism in circuit opening position and manual means extending through said second mentioned wall to release the latch means.

4. In a control switch having pressure safety mechanism, a switch arm, an auxiliary switch arm, a spring connection between said switch arms to provide substantially constant contact pressure between the contacts controlled by said switch arm when said auxiliary switch arm is in closed circuit position, and means operable to throw said switch arm to widely open circuit position against the bias of said spring when said auxiliary switch arm is in closed circuit position, said last means comprising toggle mechanism responsive to abnormal pressure and means to latch said toggle mechanism in circuit opening position, said last means permitting return of said switch arm to closely adjacent closed circuit position.

5. In a control switch having abnormal pressure safety mechanism, a switch arm, an auxiliary switch arm, means restraining both of said switch arms to assume a closed circuit position, spring means operable to retain said auxiliary switch arm in open circuit position against the bias of said first means when said auxiliary switch arm is moved to open circuit position, a resilient connection between said switch arm and said auxiliary switch arm whereby said switch arm can be thrown to a wide open circuit position, said resilient connection being comparatively light to permit of such throwing and thereafter effecting return of said switch" arm to a permitted position, pressure responsive means normally operable to move said auxiliary switch arm between open and closed circuit positions, a second pressure responsive means responding to an abnormal pressure to so throw the switch arm to said wide open circuit position against the constraint of said resilient connection, said second pressure responsive means then being in position to limit said switch arm upon its return to said permitted position with the switch contacts closely adjacent each other, and means to reset said second pressure responsive means after the abnormal pressure has returned to normal.

6. In a control switch havinghigh pressure safety mechanism, a switch arm, pressure responsive means to move said switch arms alternately to closed and open circuit positions in response to rise and fall in the pressure aifecting said pressure responsive means, means operable to move said switch arm to open circuit position independent of said pressure responsive means, said last means being responsive to an abnormally high pressure and including toggle mechanismengageable with said switch arm to throw it to widely open circuit position, a latch for latching said toggle mechanism in circuit opening position, said latch permitting return of the switch to closely adjacent closed circuit position and a reset button operable to release said latch 

